# encoding:utf-8
# @文件: whoosh_cn_backend.py
# @创建者：州的先生
# #日期：2020/11/22
# 博客地址：zmister.com

import json
import os
import re
import shutil
import threading
import warnings

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.utils.datetime_safe import datetime
from django.utils.encoding import force_str

from haystack.backends import (
    BaseEngine,
    BaseSearchBackend,
    BaseSearchQuery,
    EmptyResults,
    log_query,
)
from haystack.constants import (
    DJANGO_CT,
    DJANGO_ID,
    FUZZY_WHOOSH_MAX_EDITS,
    FUZZY_WHOOSH_MIN_PREFIX,
    ID,
)
from haystack.exceptions import MissingDependency, SearchBackendError, SkipDocument
from haystack.inputs import Clean, Exact, PythonData, Raw
from haystack.models import SearchResult
from haystack.utils import get_identifier, get_model_ct
from haystack.utils import log as logging
from haystack.utils.app_loading import haystack_get_model

try:
    import whoosh
except ImportError:
    raise MissingDependency(
        "The 'whoosh' backend requires the installation of 'Whoosh'. Please refer to the documentation."
    )

# Handle minimum requirement.
if not hasattr(whoosh, "__version__") or whoosh.__version__ < (2, 5, 0):
    raise MissingDependency("The 'whoosh' backend requires version 2.5.0 or greater.")

# Bubble up the correct error.
from whoosh import index
# from whoosh.analysis import StemmingAnalyzer
from app_doc.search.chinese_analyzer import ChineseAnalyzer as StemmingAnalyzer
from whoosh.fields import ID as WHOOSH_ID
from whoosh.fields import (
    BOOLEAN,
    DATETIME,
    IDLIST,
    KEYWORD,
    NGRAM,
    NGRAMWORDS,
    NUMERIC,
    Schema,
    TEXT,
)
from whoosh.filedb.filestore import FileStorage, RamStorage
from whoosh.highlight import highlight as whoosh_highlight
from whoosh.highlight import ContextFragmenter, HtmlFormatter
from whoosh.qparser import QueryParser, FuzzyTermPlugin
from whoosh.searching import ResultsPage
from whoosh.writing import AsyncWriter


DATETIME_REGEX = re.compile(
    "^(?P<year>\d{4})-(?P<month>\d{2})-(?P<day>\d{2})T(?P<hour>\d{2}):(?P<minute>\d{2}):(?P<second>\d{2})(\.\d{3,6}Z?)?$"
)
LOCALS = threading.local()
LOCALS.RAM_STORE = None


class WhooshHtmlFormatter(HtmlFormatter):
    """
    This is a HtmlFormatter simpler than the whoosh.HtmlFormatter.
    We use it to have consistent results across backends. Specifically,
    Solr, Xapian and Elasticsearch are using this formatting.
    """

    template = "<%(tag)s>%(t)s</%(tag)s>"


class WhooshSearchBackend(BaseSearchBackend):
    # Word reserved by Whoosh for special use.
    RESERVED_WORDS = ("AND", "NOT", "OR", "TO")

    # Characters reserved by Whoosh for special use.
    # The '\\' must come first, so as not to overwrite the other slash replacements.
    RESERVED_CHARACTERS = (
        "\\",
        "+",
        "-",
        "&&",
        "||",
        "!",
        "(",
        ")",
        "{",
        "}",
        "[",
        "]",
        "^",
        '"',
        "~",
        "*",
        "?",
        ":",
        ".",
    )

    def __init__(self, connection_alias, **connection_options):
        super(WhooshSearchBackend, self).__init__(
            connection_alias, **connection_options
        )
        self.setup_complete = False
        self.use_file_storage = True
        self.post_limit = getattr(connection_options, "POST_LIMIT", 128 * 1024 * 1024)
        self.path = connection_options.get("PATH")

        if connection_options.get("STORAGE", "file") != "file":
            self.use_file_storage = False

        if self.use_file_storage and not self.path:
            raise ImproperlyConfigured(
                "You must specify a 'PATH' in your settings for connection '%s'."
                % connection_alias
            )

        self.log = logging.getLogger("haystack")

    def setup(self):
        """
        Defers loading until needed.
        """
        from haystack import connections

        new_index = False

        # Make sure the index is there.
        if self.use_file_storage and not os.path.exists(self.path):
            os.makedirs(self.path)
            new_index = True

        if self.use_file_storage and not os.access(self.path, os.W_OK):
            raise IOError(
                "The path to your Whoosh index '%s' is not writable for the current user/group."
                % self.path
            )

        if self.use_file_storage:
            self.storage = FileStorage(self.path)
        else:
            global LOCALS

            if getattr(LOCALS, "RAM_STORE", None) is None:
                LOCALS.RAM_STORE = RamStorage()

            self.storage = LOCALS.RAM_STORE

        self.content_field_name, self.schema = self.build_schema(
            connections[self.connection_alias].get_unified_index().all_searchfields()
        )
        self.parser = QueryParser(self.content_field_name, schema=self.schema)
        self.parser.add_plugins([FuzzyTermPlugin])

        if new_index is True:
            self.index = self.storage.create_index(self.schema)
        else:
            try:
                self.index = self.storage.open_index(schema=self.schema)
            except index.EmptyIndexError:
                self.index = self.storage.create_index(self.schema)

        self.setup_complete = True

    def build_schema(self, fields):
        schema_fields = {
            ID: WHOOSH_ID(stored=True, unique=True),
            DJANGO_CT: WHOOSH_ID(stored=True),
            DJANGO_ID: WHOOSH_ID(stored=True),
        }
        # Grab the number of keys that are hard-coded into Haystack.
        # We'll use this to (possibly) fail slightly more gracefully later.
        initial_key_count = len(schema_fields)
        content_field_name = ""

        for field_name, field_class in fields.items():
            if field_class.is_multivalued:
                if field_class.indexed is False:
                    schema_fields[field_class.index_fieldname] = IDLIST(
                        stored=True, field_boost=field_class.boost
                    )
                else:
                    schema_fields[field_class.index_fieldname] = KEYWORD(
                        stored=True,
                        commas=True,
                        scorable=True,
                        field_boost=field_class.boost,
                    )
            elif field_class.field_type in ["date", "datetime"]:
                schema_fields[field_class.index_fieldname] = DATETIME(
                    stored=field_class.stored, sortable=True
                )
            elif field_class.field_type == "integer":
                schema_fields[field_class.index_fieldname] = NUMERIC(
                    stored=field_class.stored,
                    numtype=int,
                    field_boost=field_class.boost,
                )
            elif field_class.field_type == "float":
                schema_fields[field_class.index_fieldname] = NUMERIC(
                    stored=field_class.stored,
                    numtype=float,
                    field_boost=field_class.boost,
                )
            elif field_class.field_type == "boolean":
                # Field boost isn't supported on BOOLEAN as of 1.8.2.
                schema_fields[field_class.index_fieldname] = BOOLEAN(
                    stored=field_class.stored
                )
            elif field_class.field_type == "ngram":
                schema_fields[field_class.index_fieldname] = NGRAM(
                    minsize=3,
                    maxsize=15,
                    stored=field_class.stored,
                    field_boost=field_class.boost,
                )
            elif field_class.field_type == "edge_ngram":
                schema_fields[field_class.index_fieldname] = NGRAMWORDS(
                    minsize=2,
                    maxsize=15,
                    at="start",
                    stored=field_class.stored,
                    field_boost=field_class.boost,
                )
            else:
                schema_fields[field_class.index_fieldname] = TEXT(
                    stored=True,
                    analyzer=StemmingAnalyzer(),
                    field_boost=field_class.boost,
                    sortable=True,
                )

            if field_class.document is True:
                content_field_name = field_class.index_fieldname
                schema_fields[field_class.index_fieldname].spelling = True

        # Fail more gracefully than relying on the backend to die if no fields
        # are found.
        if len(schema_fields) <= initial_key_count:
            raise SearchBackendError(
                "No fields were found in any search_indexes. Please correct this before attempting to search."
            )

        return (content_field_name, Schema(**schema_fields))

    def update(self, index, iterable, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        writer = AsyncWriter(self.index)

        for obj in iterable:
            try:
                doc = index.full_prepare(obj)
            except SkipDocument:
                self.log.debug("Indexing for object `%s` skipped", obj)
            else:
                # Really make sure it's unicode, because Whoosh won't have it any
                # other way.
                for key in doc:
                    doc[key] = self._from_python(doc[key])

                # Document boosts aren't supported in Whoosh 2.5.0+.
                if "boost" in doc:
                    del doc["boost"]

                try:
                    writer.update_document(**doc)
                except Exception as e:
                    if not self.silently_fail:
                        raise

                    # We'll log the object identifier but won't include the actual object
                    # to avoid the possibility of that generating encoding errors while
                    # processing the log message:
                    self.log.error(
                        "%s while preparing object for update" % e.__class__.__name__,
                        exc_info=True,
                        extra={"data": {"index": index, "object": get_identifier(obj)}},
                    )

        if len(iterable) > 0:
            # For now, commit no matter what, as we run into locking issues otherwise.
            writer.commit()

    def remove(self, obj_or_string, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        whoosh_id = get_identifier(obj_or_string)

        try:
            self.index.delete_by_query(q=self.parser.parse('%s:"%s"' % (ID, whoosh_id)))
        except Exception as e:
            if not self.silently_fail:
                raise

            self.log.error(
                "Failed to remove document '%s' from Whoosh: %s",
                whoosh_id,
                e,
                exc_info=True,
            )

    def clear(self, models=None, commit=True):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()

        if models is not None:
            assert isinstance(models, (list, tuple))

        try:
            if models is None:
                self.delete_index()
            else:
                models_to_delete = []

                for model in models:
                    models_to_delete.append("%s:%s" % (DJANGO_CT, get_model_ct(model)))

                self.index.delete_by_query(
                    q=self.parser.parse(" OR ".join(models_to_delete))
                )
        except Exception as e:
            if not self.silently_fail:
                raise

            if models is not None:
                self.log.error(
                    "Failed to clear Whoosh index of models '%s': %s",
                    ",".join(models_to_delete),
                    e,
                    exc_info=True,
                )
            else:
                self.log.error("Failed to clear Whoosh index: %s", e, exc_info=True)

    def delete_index(self):
        # Per the Whoosh mailing list, if wiping out everything from the index,
        # it's much more efficient to simply delete the index files.
        if self.use_file_storage and os.path.exists(self.path):
            shutil.rmtree(self.path)
        elif not self.use_file_storage:
            self.storage.clean()

        # Recreate everything.
        self.setup()

    def optimize(self):
        if not self.setup_complete:
            self.setup()

        self.index = self.index.refresh()
        self.index.optimize()

    def calculate_page(self, start_offset=0, end_offset=None):
        # Prevent against Whoosh throwing an error. Requires an end_offset
        # greater than 0.
        if end_offset is not None and end_offset <= 0:
            end_offset = 1

        # Determine the page.
        page_num = 0

        if end_offset is None:
            end_offset = 1000000

        if start_offset is None:
            start_offset = 0

        page_length = end_offset - start_offset

        if page_length and page_length > 0:
            page_num = int(start_offset / page_length)

        # Increment because Whoosh uses 1-based page numbers.
        page_num += 1
        return page_num, page_length

    @log_query
    def search(
        self,
        query_string,
        sort_by=None,
        start_offset=0,
        end_offset=None,
        fields="",
        highlight=False,
        facets=None,
        date_facets=None,
        query_facets=None,
        narrow_queries=None,
        spelling_query=None,
        within=None,
        dwithin=None,
        distance_point=None,
        models=None,
        limit_to_registered_models=None,
        result_class=None,
        **kwargs
    ):
        if not self.setup_complete:
            self.setup()

        # A zero length query should return no results.
        if len(query_string) == 0:
            return {"results": [], "hits": 0}

        query_string = force_str(query_string)

        # A one-character query (non-wildcard) gets nabbed by a stopwords
        # filter and should yield zero results.
        if len(query_string) <= 1 and query_string != "*":
            return {"results": [], "hits": 0}

        reverse = False

        if sort_by is not None:
            # Determine if we need to reverse the results and if Whoosh can
            # handle what it's being asked to sort by. Reversing is an
            # all-or-nothing action, unfortunately.
            sort_by_list = []
            reverse_counter = 0

            for order_by in sort_by:
                if order_by.startswith("-"):
                    reverse_counter += 1

            if reverse_counter and reverse_counter != len(sort_by):
                raise SearchBackendError(
                    "Whoosh requires all order_by fields"
                    " to use the same sort direction"
                )

            for order_by in sort_by:
                if order_by.startswith("-"):
                    sort_by_list.append(order_by[1:])

                    if len(sort_by_list) == 1:
                        reverse = True
                else:
                    sort_by_list.append(order_by)

                    if len(sort_by_list) == 1:
                        reverse = False

            sort_by = sort_by_list

        if facets is not None:
            warnings.warn("Whoosh does not handle faceting.", Warning, stacklevel=2)

        if date_facets is not None:
            warnings.warn(
                "Whoosh does not handle date faceting.", Warning, stacklevel=2
            )

        if query_facets is not None:
            warnings.warn(
                "Whoosh does not handle query faceting.", Warning, stacklevel=2
            )

        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(
                settings, "HAYSTACK_LIMIT_TO_REGISTERED_MODELS", True
            )

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(
                " OR ".join(["%s:%s" % (DJANGO_CT, rm) for rm in model_choices])
            )

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(
                    self.parser.parse(force_str(nq)), limit=None
                )

                if len(recent_narrowed_results) <= 0:
                    return {"results": [], "hits": 0}

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                    narrowed_results = recent_narrowed_results

        self.index = self.index.refresh()

        if self.index.doc_count():
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query_string)

            # In the event of an invalid/stopworded query, recover gracefully.
            if parsed_query is None:
                return {"results": [], "hits": 0}

            page_num, page_length = self.calculate_page(start_offset, end_offset)

            search_kwargs = {
                "pagelen": page_length,
                "sortedby": sort_by,
                "reverse": reverse,
            }

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None:
                search_kwargs["filter"] = narrowed_results

            try:
                raw_page = searcher.search_page(parsed_query, page_num, **search_kwargs)
            except ValueError:
                if not self.silently_fail:
                    raise

                return {"results": [], "hits": 0, "spelling_suggestion": None}

            # Because as of Whoosh 2.5.1, it will return the wrong page of
            # results if you request something too high. :(
            if raw_page.pagenum < page_num:
                return {"results": [], "hits": 0, "spelling_suggestion": None}

            results = self._process_results(
                raw_page,
                highlight=highlight,
                query_string=query_string,
                spelling_query=spelling_query,
                result_class=result_class,
            )
            searcher.close()

            if hasattr(narrow_searcher, "close"):
                narrow_searcher.close()

            return results
        else:
            if self.include_spelling:
                if spelling_query:
                    spelling_suggestion = self.create_spelling_suggestion(
                        spelling_query
                    )
                else:
                    spelling_suggestion = self.create_spelling_suggestion(query_string)
            else:
                spelling_suggestion = None

            return {
                "results": [],
                "hits": 0,
                "spelling_suggestion": spelling_suggestion,
            }

    def more_like_this(
        self,
        model_instance,
        additional_query_string=None,
        start_offset=0,
        end_offset=None,
        models=None,
        limit_to_registered_models=None,
        result_class=None,
        **kwargs
    ):
        if not self.setup_complete:
            self.setup()

        field_name = self.content_field_name
        narrow_queries = set()
        narrowed_results = None
        self.index = self.index.refresh()

        if limit_to_registered_models is None:
            limit_to_registered_models = getattr(
                settings, "HAYSTACK_LIMIT_TO_REGISTERED_MODELS", True
            )

        if models and len(models):
            model_choices = sorted(get_model_ct(model) for model in models)
        elif limit_to_registered_models:
            # Using narrow queries, limit the results to only models handled
            # with the current routers.
            model_choices = self.build_models_list()
        else:
            model_choices = []

        if len(model_choices) > 0:
            if narrow_queries is None:
                narrow_queries = set()

            narrow_queries.add(
                " OR ".join(["%s:%s" % (DJANGO_CT, rm) for rm in model_choices])
            )

        if additional_query_string and additional_query_string != "*":
            narrow_queries.add(additional_query_string)

        narrow_searcher = None

        if narrow_queries is not None:
            # Potentially expensive? I don't see another way to do it in Whoosh...
            narrow_searcher = self.index.searcher()

            for nq in narrow_queries:
                recent_narrowed_results = narrow_searcher.search(
                    self.parser.parse(force_str(nq)), limit=None
                )

                if len(recent_narrowed_results) <= 0:
                    return {"results": [], "hits": 0}

                if narrowed_results:
                    narrowed_results.filter(recent_narrowed_results)
                else:
                    narrowed_results = recent_narrowed_results

        page_num, page_length = self.calculate_page(start_offset, end_offset)

        self.index = self.index.refresh()
        raw_results = EmptyResults()

        searcher = None
        if self.index.doc_count():
            query = "%s:%s" % (ID, get_identifier(model_instance))
            searcher = self.index.searcher()
            parsed_query = self.parser.parse(query)
            results = searcher.search(parsed_query)

            if len(results):
                raw_results = results[0].more_like_this(field_name, top=end_offset)

            # Handle the case where the results have been narrowed.
            if narrowed_results is not None and hasattr(raw_results, "filter"):
                raw_results.filter(narrowed_results)

        try:
            raw_page = ResultsPage(raw_results, page_num, page_length)
        except ValueError:
            if not self.silently_fail:
                raise

            return {"results": [], "hits": 0, "spelling_suggestion": None}

        # Because as of Whoosh 2.5.1, it will return the wrong page of
        # results if you request something too high. :(
        if raw_page.pagenum < page_num:
            return {"results": [], "hits": 0, "spelling_suggestion": None}

        results = self._process_results(raw_page, result_class=result_class)

        if searcher:
            searcher.close()

        if hasattr(narrow_searcher, "close"):
            narrow_searcher.close()

        return results

    def _process_results(
        self,
        raw_page,
        highlight=False,
        query_string="",
        spelling_query=None,
        result_class=None,
    ):
        from haystack import connections

        results = []

        # It's important to grab the hits first before slicing. Otherwise, this
        # can cause pagination failures.
        hits = len(raw_page)

        if result_class is None:
            result_class = SearchResult

        facets = {}
        spelling_suggestion = None
        unified_index = connections[self.connection_alias].get_unified_index()
        indexed_models = unified_index.get_indexed_models()

        for doc_offset, raw_result in enumerate(raw_page):
            score = raw_page.score(doc_offset) or 0
            app_label, model_name = raw_result[DJANGO_CT].split(".")
            additional_fields = {}
            model = haystack_get_model(app_label, model_name)

            if model and model in indexed_models:
                for key, value in raw_result.items():
                    index = unified_index.get_index(model)
                    string_key = str(key)

                    if string_key in index.fields and hasattr(
                        index.fields[string_key], "convert"
                    ):
                        # Special-cased due to the nature of KEYWORD fields.
                        if index.fields[string_key].is_multivalued:
                            if value is None or len(value) is 0:
                                additional_fields[string_key] = []
                            else:
                                additional_fields[string_key] = value.split(",")
                        else:
                            additional_fields[string_key] = index.fields[
                                string_key
                            ].convert(value)
                    else:
                        additional_fields[string_key] = self._to_python(value)

                del (additional_fields[DJANGO_CT])
                del (additional_fields[DJANGO_ID])

                if highlight:
                    sa = StemmingAnalyzer()
                    formatter = WhooshHtmlFormatter("em")
                    terms = [token.text for token in sa(query_string)]

                    whoosh_result = whoosh_highlight(
                        additional_fields.get(self.content_field_name),
                        terms,
                        sa,
                        ContextFragmenter(),
                        formatter,
                    )
                    additional_fields["highlighted"] = {
                        self.content_field_name: [whoosh_result]
                    }

                result = result_class(
                    app_label,
                    model_name,
                    raw_result[DJANGO_ID],
                    score,
                    **additional_fields
                )
                results.append(result)
            else:
                hits -= 1

        if self.include_spelling:
            if spelling_query:
                spelling_suggestion = self.create_spelling_suggestion(spelling_query)
            else:
                spelling_suggestion = self.create_spelling_suggestion(query_string)

        return {
            "results": results,
            "hits": hits,
            "facets": facets,
            "spelling_suggestion": spelling_suggestion,
        }

    def create_spelling_suggestion(self, query_string):
        spelling_suggestion = None
        reader = self.index.reader()
        corrector = reader.corrector(self.content_field_name)
        cleaned_query = force_str(query_string)

        if not query_string:
            return spelling_suggestion

        # Clean the string.
        for rev_word in self.RESERVED_WORDS:
            cleaned_query = cleaned_query.replace(rev_word, "")

        for rev_char in self.RESERVED_CHARACTERS:
            cleaned_query = cleaned_query.replace(rev_char, "")

        # Break it down.
        query_words = cleaned_query.split()
        suggested_words = []

        for word in query_words:
            suggestions = corrector.suggest(word, limit=1)

            if len(suggestions) > 0:
                suggested_words.append(suggestions[0])

        spelling_suggestion = " ".join(suggested_words)
        return spelling_suggestion

    def _from_python(self, value):
        """
        Converts Python values to a string for Whoosh.

        Code courtesy of pysolr.
        """
        if hasattr(value, "strftime"):
            if not hasattr(value, "hour"):
                value = datetime(value.year, value.month, value.day, 0, 0, 0)
        elif isinstance(value, bool):
            if value:
                value = "true"
            else:
                value = "false"
        elif isinstance(value, (list, tuple)):
            value = ",".join([force_str(v) for v in value])
        elif isinstance(value, (int, float)):
            # Leave it alone.
            pass
        else:
            value = force_str(value)
        return value

    def _to_python(self, value):
        """
        Converts values from Whoosh to native Python values.

        A port of the same method in pysolr, as they deal with data the same way.
        """
        if value == "true":
            return True
        elif value == "false":
            return False

        if value and isinstance(value, str):
            possible_datetime = DATETIME_REGEX.search(value)

            if possible_datetime:
                date_values = possible_datetime.groupdict()

                for dk, dv in date_values.items():
                    date_values[dk] = int(dv)

                return datetime(
                    date_values["year"],
                    date_values["month"],
                    date_values["day"],
                    date_values["hour"],
                    date_values["minute"],
                    date_values["second"],
                )

        try:
            # Attempt to use json to load the values.
            converted_value = json.loads(value)

            # Try to handle most built-in types.
            if isinstance(
                converted_value,
                (list, tuple, set, dict, int, float, complex),
            ):
                return converted_value
        except:
            # If it fails (SyntaxError or its ilk) or we don't trust it,
            # continue on.
            pass

        return value


class WhooshSearchQuery(BaseSearchQuery):
    def _convert_datetime(self, date):
        if hasattr(date, "hour"):
            return force_str(date.strftime("%Y%m%d%H%M%S"))
        else:
            return force_str(date.strftime("%Y%m%d000000"))

    def clean(self, query_fragment):
        """
        Provides a mechanism for sanitizing user input before presenting the
        value to the backend.

        Whoosh 1.X differs here in that you can no longer use a backslash
        to escape reserved characters. Instead, the whole word should be
        quoted.
        """
        words = query_fragment.split()
        cleaned_words = []

        for word in words:
            if word in self.backend.RESERVED_WORDS:
                word = word.replace(word, word.lower())

            for char in self.backend.RESERVED_CHARACTERS:
                if char in word:
                    word = "'%s'" % word
                    break

            cleaned_words.append(word)
        return " ".join(cleaned_words)

    def build_query_fragment(self, field, filter_type, value):
        from haystack import connections

        query_frag = ""
        is_datetime = False

        if not hasattr(value, "input_type_name"):
            # Handle when we've got a ``ValuesListQuerySet``...
            if hasattr(value, "values_list"):
                value = list(value)

            if hasattr(value, "strftime"):
                is_datetime = True

            if isinstance(value, str) and value != " ":
                # It's not an ``InputType``. Assume ``Clean``.
                value = Clean(value)
            else:
                value = PythonData(value)

        # Prepare the query using the InputType.
        prepared_value = value.prepare(self)

        if not isinstance(prepared_value, (set, list, tuple)):
            # Then convert whatever we get back to what pysolr wants if needed.
            prepared_value = self.backend._from_python(prepared_value)

        # 'content' is a special reserved word, much like 'pk' in
        # Django's ORM layer. It indicates 'no special field'.
        if field == "content":
            index_fieldname = ""
        else:
            index_fieldname = "%s:" % connections[
                self._using
            ].get_unified_index().get_index_fieldname(field)

        filter_types = {
            "content": "%s",
            "contains": "*%s*",
            "endswith": "*%s",
            "startswith": "%s*",
            "exact": "%s",
            "gt": "{%s to}",
            "gte": "[%s to]",
            "lt": "{to %s}",
            "lte": "[to %s]",
            "fuzzy": "%s~{}/%d".format(FUZZY_WHOOSH_MAX_EDITS),
        }

        if value.post_process is False:
            query_frag = prepared_value
        else:
            if filter_type in [
                "content",
                "contains",
                "startswith",
                "endswith",
                "fuzzy",
            ]:
                if value.input_type_name == "exact":
                    query_frag = prepared_value
                else:
                    # Iterate over terms & incorportate the converted form of each into the query.
                    terms = []

                    if isinstance(prepared_value, str):
                        possible_values = prepared_value.split(" ")
                    else:
                        if is_datetime is True:
                            prepared_value = self._convert_datetime(prepared_value)

                        possible_values = [prepared_value]

                    for possible_value in possible_values:
                        possible_value_str = self.backend._from_python(
                            possible_value
                        )
                        if filter_type == "fuzzy":
                            terms.append(
                                filter_types[filter_type] % (
                                    possible_value_str,
                                    min(
                                        FUZZY_WHOOSH_MIN_PREFIX,
                                        len(possible_value_str)
                                    )
                                )
                            )
                        else:
                            terms.append(
                                filter_types[filter_type] % possible_value_str
                            )

                    if len(terms) == 1:
                        query_frag = terms[0]
                    else:
                        query_frag = "(%s)" % " AND ".join(terms)
            elif filter_type == "in":
                in_options = []

                for possible_value in prepared_value:
                    is_datetime = False

                    if hasattr(possible_value, "strftime"):
                        is_datetime = True

                    pv = self.backend._from_python(possible_value)

                    if is_datetime is True:
                        pv = self._convert_datetime(pv)

                    if isinstance(pv, str) and not is_datetime:
                        in_options.append('"%s"' % pv)
                    else:
                        in_options.append("%s" % pv)

                query_frag = "(%s)" % " OR ".join(in_options)
            elif filter_type == "range":
                start = self.backend._from_python(prepared_value[0])
                end = self.backend._from_python(prepared_value[1])

                if hasattr(prepared_value[0], "strftime"):
                    start = self._convert_datetime(start)

                if hasattr(prepared_value[1], "strftime"):
                    end = self._convert_datetime(end)

                query_frag = "[%s to %s]" % (start, end)
            elif filter_type == "exact":
                if value.input_type_name == "exact":
                    query_frag = prepared_value
                else:
                    prepared_value = Exact(prepared_value).prepare(self)
                    query_frag = filter_types[filter_type] % prepared_value
            else:
                if is_datetime is True:
                    prepared_value = self._convert_datetime(prepared_value)

                query_frag = filter_types[filter_type] % prepared_value

        if len(query_frag) and not isinstance(value, Raw):
            if not query_frag.startswith("(") and not query_frag.endswith(")"):
                query_frag = "(%s)" % query_frag

        return "%s%s" % (index_fieldname, query_frag)


class WhooshEngine(BaseEngine):
    backend = WhooshSearchBackend
    query = WhooshSearchQuery
